fix(deals): restore "Command Code" sidebar for Ox Alpha and DeepSeek V4 Flash Vision (exp) (issue #61)

The Deals catalog had no entries for stealth/ox-alpha and
deepseek/deepseek-v4-flash-vision-exp, so enrichment never injected
options.cmd and the TUI sidebar section silently rendered nothing.
Both models entered the Snapshot in recent catalog refreshes but the
docs fixtures predated them.

- Re-capture goat/pro fixtures from the live docs (adds the two records)
- Regenerate src/deals/catalog.ts with the new entries
- Add a coverage gate to refresh-deals.mjs: abort (exit 1) when the
  scraped/fixture records lack a Snapshot model, so a partial catalog
  can never be emitted silently; --allow-partial opts out for the
  release pipeline's non-blocking check
- Add scripts/check-deals-coverage.mjs standalone pre-commit check
- Add tests/deals-coverage.test.ts regression coverage
- Add .opencode/skills/refresh SKILL.md for the refresh workflow
- Update release workflow, AGENTS.md, CONTEXT.md docs